1. Field of the Invention
The present invention relates to a semiconductor device having a bump electrode as an electrode for inputting and outputting signals to and from a semiconductor element and a method for manufacturing the same, and in particular to a semiconductor device which can suppress occurrence of cracks at an area below the bump electrode upon the bonding of an inner lead and can achieve an enhanced heat resistance cycle property after the inner lead bonding has been carried out and a method for manufacturing the same.
2. Description of the Related Art
Conventionally bump electrodes have been employed as those electrodes for a TAB type and a COB (chip on board) type semiconductor device.
FIGS. 1 to 3, each, are a cross-sectional view showing a major section of a semiconductor device having a conventional bump electrode. This structure is disclosed, for example, in Published Unexamined Japanese Patent Application H-1-1640401, but involves drawbacks as will be set out below.
As shown in FIG. 1, a bump electrode 102 is provided on a semiconductor substrate 101. A resin film 103 is covered over the surface of the semiconductor substrate 101 except at the bump electrode 102. The surface of the resin film 103 is flush with that of the bump electrode 102 at an area 105 adjacent the bump electrode 102. The resin film 103 serves as a film for protection against any external mechanical damage due to a dicing process, etc., and can prevent a lead shorting whereby direct lead-to-substrate contact occurs. However, the aforementioned semiconductor structure has the following drawbacks. To be specific, upon the bonding of the lead to the device shown in FIG. 2, the lead 107 is pushed with a pressure P by a bonding tool 106, causing the lead 107 to be pushed into the bump electrode 102. At this time, the bump electrode 102 is deformed so that a crack occurs in the resin film 103 as indicated by reference numeral 108. There is a fear that, upon the occurrence of such a crack in the resin film 103, water and harmful impurities will intrude into the substrate (device body) 101 via the crack 108. This adversely affects the device reliability.
FIG. 3 is a cross-sectional view, as taken along line IIIxe2x80x94III in FIG. 2. As shown in FIG. 3, the lead 107 makes direct contact with the resin film 103 in the semiconductor device of FIG. 1. In this state, upon the thermocompression bonding of the lead 107 to the device, heat is transmitted via the lead 107 to the resin film 103 to cause the resin film 103 to be affected by the heat at an area (heat-affected area) indicated by reference numeral 109 in FIG. 3. The resin film 103, being so heat-affected, gives a bad effect to the device reliability. In addition to the aforementioned drawbacks encountered upon the pushing of the lead onto the bump electrode and upon the thermocompression bonding, an eutectic alloy, i.e., an alloy of tin (Sn) plated to the surface of the lead 107 and gold (Au) contained in the bump electrode 102, is not adequately formed due to the lead 107 contacting with the resin film 103 upon the pushing of the lead 107 into the bump electrode 102. As a result, the lead 107 is liable to be separated off the bump electrode 102.
It is accordingly the object of the present invention to provide a semiconductor device which can suppress occurrence of cracks at an area below a bump electrode upon the bonding of an inner lead and can achieve an enhanced heat resistance cycle property after the bonding of the inner lead and a method for manufacturing the same.
According to one aspect of the present invention there is provided a semiconductor device comprising a semiconductor substrate, at least one bump electrode provided over the semiconductor substrate to allow signals to be input and output to and from a semiconductor device, and a resin film covered on a surface of the semiconductor substrate except at a top area of the bump electrode, wherein the top area of the bump electrode is more projected than a top area of the resin film.
According to another aspect of the present invention there is provided a method for manufacturing a semiconductor device comprising the steps of forming at least one electrode pad over a semiconductor substrate, providing an opening in a surface portion of the electrode pad and forming a passivation film over a surface of the semiconductor substrate and that of the electrode pad, forming a metal film over the surface of the electrode pad at an area of the opening and over the passivation film near the opening, providing a bump electrode over the metal layer, forming an organic insulating film over the bump electrode and passivation film, and etching back the organic insulating film to allow a top area of the bump electrode to be more projected than a top area of the organic insulating film.
The present device and method can suppress occurrence of cracks at an area below a bump electrode upon the bonding of an inner lead and can achieve an enhanced heat resistance cycle property after the bonding of the inner lead.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particuarly pointed out in the appended claims.